Halftone image recording method and apparatus

Abstract

A halftone image recording apparatus has an interpolating function for interpolating previously obtained first halftone pattern data in the main scanning direction to obtain second halftone pattern data. Comparisons between input image signals and the second halftone pattern data per pixel are made to expose a photosensitive material on the basis of the results of the comparisons thereby to create a halftone plate. Through the interpolation, the recording density in the main scanning direction is increased in response to the rate of increase in pixel density.

What is claimed is: 
     
       1. A halftone image recording apparatus for creating a halftone plate by sequentially making comparisons of input image signals to be recorded with halftone pattern data, along scanning directions, pixel by pixel, said halftone pattern data given for indicating a regular and repetitive screen pattern defined to express a screen structure in halftone dot image recording and outputting halftone dot recording signals responsive to the results of said comparisons, said halftone image recording apparatus comprising: first memory means for storing first halftone pattern data;   interpolation means for reading said first halftone pattern data from said first memory means and interpolating said first halftone pattern data in the main scanning direction to obtain second halftone pattern data;   comparator means for sequentially comparing said input image signals with said second halftone pattern data pixel-by-pixel at a timing responsive to the rate of increase in pixel density in the main scanning direction through interpolation by said interpolation means and, in response, outputting halftone dot recording signals; and   exposure means for scanning and exposing a prescribed photosensitive material in response to said halftone dot recording signals to create a halftone plate increased in recording density in the main scanning direction in accordance with the rate of increase in pixel density through said interpolation.   
     
     
       2. A halftone image recording apparatus in accordance with claim 1, wherein said exposure means generates an exposure beam having a spot diameter of a size corresponding to the recording pixel density in the sub-scanning direction.   
     
     
       3. A halftone image recording apparatus in accordance with claim 1, wherein said interpolation means includes means for obtaining said second halftone pattern data prestored in a second memory means, to be read from said second memory means for development of said recording signals.   
     
     
       4. A halftone image recording apparatus in accordance with claim 1, wherein said second interpolation means includes means for obtaining said halftone pattern data simultaneously with exposure of said photosensitive material by said scanning means.   
     
     
       5. A halftone image recording apparatus for creating a halftone plate by sequentially making comparisons between input image signals to be recorded and halftone pattern data along scanning directions, pixel-by-pixel, said halftone pattern data given for indicating a regular and repetitive screen pattern defined to express a screen structure in halftone dot image recording and outputting halftone dot recording signals responsive to the results of said comparisons, said halftone image recording apparatus comprising: first memory means for storing predetermined first halftone pattern data corresponding to respective ones of a prescribed number of types of screen structures;   screen structure selecting means for selecting a desired screen structure from said prescribed number of types of screen structures;   interpolation means for reading said first halftone pattern data from said memory means and interpolating said first halftone pattern data in the main scanning direction when said desired screen structure selected by said screen structure selecting means is that of a prescribed type, thereby to obtain second halftone pattern data;   comparator means for sequentially making comparisons of said input image signals with said second halftone pattern data, pixel-by-pixel at a timing responsive to the rate of increase in pixel density in the main scanning direction through said interpolation to output halftone dot recording signals responsive to the results of said comparisons; and   exposure means for scanning and exposing a prescribed photosensitive material in response to said halftone dot recording signals to create a halftone plate increased in recording density in the main scanning direction in response to the rate of said increase in pixel density through an interpolation by said interpolation means.   
     
     
       6. A halftone image recording apparatus in accordance with claim 5, wherein said exposure means includes means for generating an exposure light beam and for varying the size of the spot diameter of said beam in accordance with the recording pixel density in the sub-scanning direction.   
     
     
       7. A halftone image recording apparatus in accordance with claim 6, wherein within said first halftone pattern data corresponding to respective ones of said screen structure types, data with respect to those having a common relation between said selected spot diameter and said screen structure, the apparatus further including means for storing said data, having a common relation in said memory means as common data.   
     
     
       8. A halftone image recording apparatus in accordance with claim 5, wherein said interpolation means includes means for obtaining said second halftone pattern data prior to image recording and stored in second memory means, to be read from said second memory means as said recording signals.   
     
     
       9. A halftone image recording apparatus in accordance with claim 5, wherein said interpolation means includes means for obtaining said second halftone pattern data simultaneously with exposing said photosensitive material by said exposure means.   
     
     
       10. A halftone image recording apparatus for creating a halftone plate by sequentially making comparisons of input image signals to be recorded with halftone pattern data, along scanning directions, pixel-by-pixel, said halftone pattern data given for indicating a regular and repetitive screen pattern to express a screen structure in halftone dot image recording, an outputting halftone dot recording signals responsive to the results of said comparisons, said halftone image recording apparatus comprising: memory means for storing predetermined first halftone pattern data in correspondence to respective ones of a prescribed number of types of screen structures;   screen structure selecting means for selecting a desired screen structure from said prescribed number of types of screen structures;   interpolation means for reading said first halftone pattern data from said memory means to interpolate said first halftone pattern data in the main scanning direction when said desired screen structure selected by said screen structure selecting means is that of a prescribed type;   comparator means for sequentially obtaining comparisons of said input image signals with said second halftone pattern data, pixel-by-pixel, at a timing responsive to the rate of increase in pixel density in the main scanning direction in accordance with interpolations by said interpolations means to output halftone dot recording signals responsive to the results of said comparisons; and   exposure means for scanning and exposing a prescribed photosensitive material in response to said halftone dot recording signals to create a halftone plate increased in recording density in the main scanning direction in response to the rate of increase in pixel density through interpolation by said interpolation means;   said first and second halftone pattern data with respect to a specific screen structure being provided in the unit of a region larger than the minimum region formed by a plurality of halftone dots and satisfying a prescribed repeating rule in both main and sub-scanning directions.   
     
     
       11. A halftone image recording apparatus in accordance with claim 10, wherein said exposure means includes means for generating an exposure light beam and for varying the size of a spot diameter of the exposure light beam responsive to a recording pixel density in a sub-scanning direction.   
     
     
       12. A halftone image recording apparatus in accordance with claim 11, wherein within said first halftone pattern data corresponding to respective ones of said screen structure types, data with respect to those having a common relation between said selected spot diameter and said screen structure, the apparatus further includes means for storing said data having a common relation in said memory means as common data.   
     
     
       13. A halftone image recording apparatus in accordance with claim 10, wherein said interpolation means includes means for obtaining said second halftone pattern data prior to image recording and stored in second memory means, to be read from said second memory means.   
     
     
       14. A halftone image recording apparatus with claim 10, wherein said interpolation means includes means for obtaining said second halftone pattern data during exposing of said photosensitive material by said exposure means.   
     
     
       15. A halftone image recording method, comprising the steps of: storing first halftone pattern data;   interpolating said first halftone pattern data in a main scanning direction to obtain second halftone pattern data for recording said halftone image on a photosensitive material;   said first halftone pattern data provided for indicating a regular and repetitive screen pattern defined to express a screen structure in halftone dot image recording;   sequentially comparing said input image signals with said second halftone pattern data, pixel-by-pixel, at a timing responsive to a rate of increase in pixel density in the main scanning direction;   in response to comparisons obtained during said comparing step, outputting halftone dot recording signals; and   scanning and exposing said photosensitive material in response to said recording signals.   
     
     
       16. The method as defined in claim 15, wherein said scanning and exposing step includes generating an exposure light beam and controlling the diameter of said beem in accordance with recording pixel density in a sub-scanning direction. 
     
     
       17. The method of claim 15, including storing said second halftone pattern data prior to said scanning and exposing step. 
     
     
       18. The method as defined in claim 15, including obtaining said second halftone pattern data simultaneously with said scanning and exposing step. 
     
     
       19. A halftone image recording method, comprising the steps of: storing predetermined first halftone pattern data corresponding to respective ones of a prescribed number of types of screen structures;   said first halftone pattern data provided for indicating a regular and repetitive screen pattern defined to express a screen structure in halftone dot image recording;   selecting a desired screen structure from said prescribed number of types of screen structures;   interpolating said first halftone pattern data in a main scanning direction when the desired screen structure selected is that of a prescribed type;   sequentially comparing input image signals with the second halftone pattern data, pixel-by-pixel, at a timing responsive to a rate of increase in pixel density in the main scanning direction through interpolation during said interpolating step to develop halftone dot recording signals; and   exposing a photosensitive recording medium in accordance with said recording signals to create a halftone plate.   
     
     
       20. The method of claim 19, wherein the exposing step includes generating an exposure light beam and controlling the diameter of said beam in accordance with a recording pixel density in a subscanning direction. 
     
     
       21. The method of claim 20, wherein: within said first halftone pattern data corresponding to respective ones of said screen structure types, data with respect to those types having a common relation between said selected beam diameter and said screen structure being stored as common data.   
     
     
       22. The method of claim 19, including storing said second halftone pattern data prior to image recording. 
     
     
       23. The method of claim 19, including obtaining said second halftone pattern data simultaneously with image recording. 
     
     
       24. A halftone image recording method, comprising the steps of: storing predetermined first halftone pattern data corresponding to respective screen structures;   said first halftone pattern data provided for indicating a regular and repetitive screen pattern defined to express a screen structure in halftone dot image recording;   selecting a desired screen structure from among said respective screen structures;   interpolating said first halftone pattern data in a main scanning direction when the desired screen structure selected is that of a predetermined type;   providing the first and second halftone pattern data with respect to a specific screen structure in the unit of a region larger than the minimum region formed by a plurality of halftone dots and satisfying a prescribed repeating rule in both main and sub-scanning directions;   sequentially comparing input image signals with the second halftone pattern data, pixel-by-pixel, at a timing responsive to a rate of increase in pixel density in the main scanning direction through interpolation during said interpolation step to develop halftone dot recording signals; and   exposing a photosensitive material in response to said recording signal.   
     
     
       25. The method as defined in claim 24, wherein said exposing step includes generating an exposing light beam and controlling the diameter of said beam in response to a recording pixel density in a sub-scanning direction. 
     
     
       26. The method as defined in claim 24, wherein: within said first halftone pattern data corresponding to respective ones of said screen structure types, data with respect to those having a common relation between said selected spot diameter and said screen structure are stored as common data.   
     
     
       27. The method as defined in claim 24, including storing said second halftone pattern data prior to image recoring. 
     
     
       28. The method as defined in claim 24, including obtaining said second halftone pattern data during image recording.